1. Field of the Invention
The present invention relates to a clamping plate capable of clamping a disk-shaped medium by attracting the medium e.g., by a drive shaft of a disk drive, a cartridge case including the clamping plate, an information medium including the cartridge case and the disk-shaped medium, a mold for manufacturing the clamping plate, and a method of manufacturing the clamping plate.
2. Description of the Related Art
As a clamping plate of this kind, there is known a clamping plate for a disk cartridge, disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2003-91955. This clamping plate is mounted on an inner side of an upper shell as a component of a cartridge housing via a clamping plate holder, such that the clamping plate is movable in a vertical direction. Further, when the disk cartridge is loaded in an information recording/reproducing device, the clamping plate is magnetically attracted toward a turntable of the information recording/reproducing device to thereby clamp a disk-shaped recording medium accommodated within the cartridge housing on the turntable. In this case, the clamping plate is comprised of a circular bottom formed by pressing a magnetic metal plate made e.g., of stainless steel, a frustoconical peripheral wall formed along the outer periphery of the bottom, and a flange portion provided on a large-diameter side of the peripheral wall. Further, a frustoconical recess into which the foremost end of a shaft of the turntable is inserted is formed in a central portion of the bottom, and an annular protrusion for holding the surface of the disk-shaped recording medium is formed on the periphery of the bottom.